The present invention relates to a book pressing machine having a pressing station for pressing a book cover on to a book block.
After the book block has been inserted into the book cover a permanent contact between the front and back end papers of the book block and the book cover without cavities is obtained by pressing the book. In industrial book production this work process of all-over pressing is carried out in fold-forming and pressing machines in combination with the fold-forming process in which the folds of the book cover are formed and glued.
Known from DE 37 33 435 A1 is a fold-forming and pressing machine which comprises a loading station, a plurality of fold-forming and pressing stations and an unloading station, books freshly inserted in an upstream book insertion machine and fed therefrom by a continuous conveyor with their spines leading being distributed to the individual fold-forming and pressing stations where a single fold-forming and pressing process is carried out with the book lying flat. Each of the fold-forming and pressing stations has a horizontally arranged pressing table and a vertically movable pressing plate for all-over pressing, a pair of vertically movable fold-forming rails for fold formation, a shaping element acting against the front edge of the book block, a two-part shaping rail for the book spine and an endless conveyor belt which conveys the book in and out and the sections of which enclose the pressing table in such a way that the upper belt section rests on the upper face of the pressing table as a support for the book.
The book is transported through the fold-forming and pressing station in the longitudinal direction of the spine, so that for entry to these stations re-orienting of the book is required. To align the book with respect to the fold-forming rails arranged laterally beside the conveyor belt and in the longitudinal direction of the conveyor a transverse displacement is also required, which is carried out by means of the shaping element acting on the front edge of the book block between the pressing table and the pressing plate. These re-orientations and transverse displacements of the freshly-assembled book sometimes cause a change in the relative positions of book cover and book block, so that the quality of the book after fold-forming and pressing is endangered. In the case of some cover materials in conjunction with the all-over pressing of the upper cover board by the pressing plate, this cover board adheres to the pressing plate as the latter opens. This leads to malfunctions in conveying the book out.
Known from DE 197 48 832 A1 is a book forming and pressing machine in which, in a first pressing station, the cover boards of a book transported with the spine leading are pressed on to the book block, starting at a distance from the book cover folds, by rotatably driven press rollers rolling on the side surfaces of the book and, in a second station following at a distance in the transport direction of the book, the book is aligned by means of a two-part forming rail movable into the plane of motion of the book and a shaping element acting against the front edge of the book block, and is pressed in the cover folds and adjoining lateral areas by means of a pair of fold-forming rails and a pair of pressing rails. The book forming and pressing machine is characterised by its simple and cost-effective construction. The conveying of the book, which is fed from the book insertion machine while lying flat and without reorientation, is also advantageous. In the case of certain materials of the book cover and book block, however, high pressures are required to achieve cavity-free pasting of the front and back end papers to the cover, leading to curvature of the book covers during rolling and impairing the reliability of further processing.
DE 197 29 529 A1 describes a method whereby the cover fold is formed with the application of heat to the cover material before the insertion of the book block into the cover, so that the fold-forming in a separate machine used hitherto can be dispensed with. The permanent gluing of the cover fold to the book block is achieved by pressing the pre-formed cover fold against the book block when inserting the book. All-over pressing is carried out after joining book block and cover by rolling with press rollers which can optionally have a longitudinal groove for pressing directly on the book fold. What was said above regarding pressing-on at high pressures applies here also.